Suspension systems are utilized on vehicles to provide ride comfort and desired handling characteristics. Various types of suspensions are known that utilize multi-link configurations, spring configurations, or a combination of both air spring and spring configurations.
One known suspension system comprises a multi-link (parallelogram) air suspension that is typically utilized on a front axle. This system includes three or more longitudinally extending linkages that attach the front axle to a chassis. A transverse torque rod attaches the front axle to the chassis via a cross member. The transverse torque rod is required to provide lateral stiffness to the system. The primary suspension components that support the sprung mass are air springs. Secondary roll stiffness is provided by a roll bar. This type of system is typically used as a leading arm suspension due to gear box steering systems positioned in front of the axle.
Disadvantages with this type of system include a high number of components and associated connection points. Further, the high number and types of components (e.g., the multiple longitudinal linkages, the transverse torque rod, a cross-member required to connect the torque rod to the chassis, and the roll bar) make this system very heavy.
Another type of front suspension comprises a spring suspension that includes one or more spring leaves that are attached to the front axle. The spring leaves constrain the axle longitudinally and laterally. Primary roll stiffness is provided by the spring leaves and secondary roll stiffness is provided by other spring components and roll bars. The primary suspension components are the spring leaves themselves, which support the sprung mass.
Disadvantages with this type of system include too high of a vertical rate, a higher brake diving (reaction to braking), and variations in ride height. A natural frequency, or vertical rate, of this type of system tends to be higher than a desired vertical rate. Further, ride height of the vehicle changes as the suspension (spring) is loaded, which is not desirable.
Another type of front suspension comprises a hybrid system that uses both air springs and spring leaves. The spring leaves constrain the axle longitudinally and laterally to the chassis. Primary roll stiffness is provided by a combination of the spring leaves and the air springs, while secondary roll stiffness is provided by roll bars, front spring geometry, spring bushings, other spring components, and/or torsional rigidity of the axle itself. Both the air springs and spring leaves support the sprung mass. Disadvantages with this type of system involve a higher brake diving and too high of a vertical rate as discussed above.
One example of a known rear suspension is a system that uses coil springs and/or air springs to support the sprung mass of a tandem axle. This type of system can be a leading or trailing arm configuration and can include multi-links for a parallelogram configuration. An X-linkage or torque box component provides secondary roll stiffness and lateral stiffness to the suspension and eliminates the need for a transverse torque rod. The X-linkage or torque box component has one or more bushings that pivotally connect to both the axle and a frame hanger.
All of the suspension systems set forth above require a significant amount of packaging space on the vehicle. Spring suspensions use long spring leaves to provide adequate vertical rate (frequency or ride comfort) while multi-link suspensions use cross members that are required to attach the transverse torque rods.